1. Field of the Invention
This invention relates generally to reversible drive hand tools for tightening or loosening screws, nuts, bolts and the like.
2. Description of the Prior Art
A number of hand tools have been devised in which the rotation of a handle in a clockwise direction effects a tightening of a screw, nut or bolt, whereas a reverse rotation in a counterclockwise direction will be ineffectual. Conversely, via an adjusting mechanism, the handle of the tool in such instances can be rotated in an opposite or counterclockwise direction to accomplish a loosening of the screw, nut or bolt, the rotation of the handle in a clockwise direction then being ineffectual.
For the most part, such prior art devices have involved the use of a ratchet mechanism which when appropriately adjusted enables the user to effect a tightening action when the handle is rotated clockwise without any loosening when rotated in a counterclockwise direction, and conversely to achieve a loosening action when the handle is rotated in a counterclockwise direction without any loosening action being realized when the handle under these conditions is rotated in a clockwise direction. An example of such a tool is disclosed in U.S. Pat. No. 819,536, issued on May 1, 1906, to Zachary T. Furbish for "Shifter Lock for Pawl and Ratchet Tools". The difficulty with this type of tool is that the torque must be transmitted through a relatively fragile ratchet mechanism. Still further, owing to the nature of a ratchet mechanism, the handle must be oscillated in opposite directions through a significant angle before the ratchet mechanism becomes effective to transmit torque from the handle to the shank carrying the work engaging member thereon, such as a screwdriver or a socket wrench. An angular "play" of the magnitude previously experienced can be extremely annoying. Coupled with the inability of a ratchet mechanism of limited size to transmit large amounts of torque, the tool just alluded to has not, as far as known to me, met with any great degree of success.
A widely used commercially available reversible hand tool is disclosed in U.S. Pat. No. 3,742,787, granted on July 3, 1973, to Carlton L. Whiteford for "Reversible Drive Ratchet Hand Tool with Spherical Handle". In this instance, the spherical handle is sufficiently large so as to accommodate therein a relatively rugged ratchet mechanism. To effect a reverse operation, however, it is necessary to remove the shank having the work engaging member thereon, such as a screwdriver, from a radially directed socket in the spherical handle and then reinsert the shank in a socket diametrically opposite the first socket. Owing to the relatively large diameter of the handle, a considerable amount of torque can be manually produced, but the size of the handle limits its use in confined spaces. Furthermore, having to reposition the tool shank can be somewhat bothersome.
Another type of reversible handle tool is exemplified in U.S. Pat. No. 3,332,304, issued on July 25, 1967, to Ben H. Lynn for "Reversible Socket Wrench Handle". This patent makes use of two coil springs which frictionally grip a shaft to which the tool member is attached. Here again, a problem arises with respect to the transmission of relatively large twisting forces or torque, and there can also be a certain amount of unnecessary angular movement before the convolutions of either coil spring contracts sufficiently to transmit the necessary twisting force.